Due to their outstanding heat and weather resistance and light weight, silicone rubber sponges are used for automotive parts, such as packings, gaskets, and O-rings; as sheath materials for rollers in copiers, and as sealing materials of various kinds. A number of silicone rubber sponge compositions have been proposed to date. Japanese Patent Publication No. Sho 44-461 and Japanese Patent Application Laying Open No. 7-247436, for example, teach silicone rubber sponge compositions containing thermally decomposable organic blowing agents such as azobisisobutyronitrile. However silicone rubber sponges produced from these compositions frequently have coarse cells, making it difficult to consistently produce silicone rubber sponges having fine, uniform cells. Accordingly, there is a need for a silicone rubber sponge composition having finer, more uniform cells.
It is an object of the present invention to provide a silicone rubber sponge composition that gives a silicone rubber sponge having fine, uniform cells, a silicone rubber sponge, and a process for production thereof.